CN111686810A - Preparation method of layer-by-layer self-assembled GQDs/3D-G/PANI composite film - Google Patents

Abstract

The invention discloses a method for preparing a layer-by-layer self-assembled GQDs/3D-G/PANI composite film, which belongs to the technical field of composite materials and electrocatalysis applications. The invention firstly prepares three-dimensional network graphene (3D-G) and graphene quantum dots (GQDs), and then uses GQDs to self-assemble on the 3D-G surface to prepare a GQDs/3D-G composite system. Finally, with the strong electrostatic force between the electropositive polyaniline (PANI) solution and the electronegative GQDs/3D-G composite dispersion solution and the π-π interaction between the benzene ring structures as the driving force, in the hydroxyl-functionalized ITO Layer-by-layer self-assembled GQDs/3D‑G/PANI composite films were constructed on the surface, polyaniline could be firmly attached to the 3D network graphene layer, and graphene quantum dots assisted the bonding between the 3D graphene sheets and the polyaniline particles. close contact, significantly reduced agglomeration, and _exhibited good electrochemical catalytic activity for _H2O2 .

Description

A kind of preparation method of layer-by-layer self-assembled GQDs/3D-G/PANI composite film

technical field

The invention relates to a method for preparing a layer-by-layer self-assembled GQDs/3D-G/PANI composite film, which has significant electrochemical catalytic activity for H ₂ O ₂ and belongs to the technical field of composite materials and electrocatalysis applications.

Background technique

With the rapid development of modern industry and science and technology, the primary challenge facing human development is the shortage of resources. The fossil fuels stored in the ground around the world are consumed in large quantities and face depletion, and the climate and environmental problems caused by the abuse of fossil fuels are also increasing. It appears that adverse factors such as the greenhouse effect, acid rain and other problems have begun to affect the global climate. At the same time, with the growth of the global economy and the improvement of human living standards, people's consumption and demand for energy are also expanding, which brings new requirements and challenges to the development of new, green and renewable energy.

Polyaniline (PANI), as one of the conductive polymers with a wide range of applications, has been used to composite with nanocarbon materials to achieve the purpose of improving the electrochemical or catalytic properties of materials. As for their synthesis, it is usually achieved by in-situ chemical or electrochemical polymerization of aniline/nanocarbon materials, and based on these methods, polyaniline complexed with carbon nanotubes (CNTs) or reduced graphene oxide (rGO) shows enhanced ratio capacitance and high cycling stability. In addition, the rGO/PANI composites prepared by in situ chemical oxidation or electrochemical polymerization have remarkable electrochemical catalytic activity towards H ₂ O ₂ and can be used as non-enzymatic biosensors. Even so, the performance of carbon nanomaterials/polyaniline is still considered to be significantly limited due to the aggregation of individual components, which is due to the uncontrollable high-speed polymerization of aniline during in-situ chemical polymerization or electrochemical polymerization. cause significant chain entanglement before reaching the surface of the nanocarbon material; on the other hand, the aggregation caused by the poor dispersion of the nanocarbon material and polyaniline in the aqueous system makes the nanocarbon material/polyaniline interface interaction too weak, thus reducing the composite material electrochemical performance. Therefore, maintaining the monodisperse state of nanocarbon materials and polyaniline molecules during the composite process is a key factor to reduce the aggregation of components, which can further improve the electrochemical performance of the resulting composites.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a simple, layer-by-layer self-assembled GQDs/3D-G/PANI composite thin film preparation method with excellent electrocatalytic activity. The dispersibility of structural graphene (3D-G) solves the problem of easy agglomeration in the reaction, and based on this, the layer-by-layer self-assembly with polyaniline is achieved to obtain electrochemical catalytic materials.

1. Preparation of layer-by-layer self-assembled GQDs/3D-G/PANI composite films

The preparation method of the layer-by-layer self-assembled GQDs/3D-G/PANI composite film of the present invention includes the following process steps:

(1) Preparation of 3D-G: disperse graphene oxide in water, add ammonia water to adjust the pH of the solution to 12~13, then add hydrazine hydrate, transfer to a hydrothermal reactor, and react at 180~185 ° C for 11~12 h, filter, wash, and dry to obtain three-dimensional network graphene 3D-G;

(2) Preparation of GQDs: 3D-G was dispersed in concentrated sulfuric acid, stirred in an ice-water bath, then KMnO ₄ was added, the reaction was kept constant at 150-155 °C for 24-25 h, cooled to room temperature, and then H ₂ O was added ₂ obtain a bright yellow GQDs solution, evaporate the GQDs solution to obtain a brown GQDs solid, dissolve the GQDs solid in ultrapure water, filter, dialyze, freeze-dry to obtain a graphene quantum dot GQDs powder;

(3) Preparation of GQDs/3D-G composite dispersion: Disperse 3D-G and GQDs in HCl solution (concentration: 0.01~0.015mol/L), stir evenly, adjust pH to 5~6 with ammonia water, and ultrasonically treat 20-30 min to obtain GQDs/3D-G composite dispersion;

(4) Preparation of PANI solution: add ammonium persulfate to HCl solution containing aniline monomer (concentration is 1~1.2 mol/L), stir at 0~5 °C for 24~25 h, filter, and use dilute HCl , ethanol and deionized water were washed successively, soaked in ammonia water for 10-12 h, and vacuum-dried to obtain polyaniline; polyaniline was added to N, N-dimethylacetamide, stirred for 2-2.5 h to obtain dark blue Then add it into dilute HCl and mix it evenly to obtain a stable aqueous dispersion conductive polyaniline solution;

(5) Preparation of layer-by-layer self-assembled GQDs/3D-G/PANI composite films: The hydroxyl-functionalized ITO was immersed in PANI solution for 2-2.5 h, washed with water, and dried by blowing nitrogen at room temperature. It was then immersed in the GQDs/3D-G composite dispersion for 2~2.5 h, and a layer of GQDs/3D-G/PANI was formed on the ITO, which was marked as (GQDs/3D-G/PANI) ₁ ; The upper layer self-assembles to obtain (GQDs/3D-G/PANI) _n composite films.

In step (1), the graphene oxide preparation method is as follows: ultrasonically exfoliating the expanded graphite in a DMF solution for 20-24 hours, filtering, washing and drying to obtain a liquid-phase ultrasonically exfoliated graphene sheet, and then exfoliating the graphene sheet Add to the mixed acid of concentrated sulfuric acid and concentrated phosphoric acid at 0~5℃, add KMnO ₄ under stirring, heat to 50~55℃ and stir for 11~12 h, and then add ice water and H ₂ O to it at room temperature ₂ solution, the color of the solution becomes golden, centrifuged, washed, and dried to obtain graphene oxide; the volume ratio of concentrated sulfuric acid and concentrated phosphoric acid in the mixed acid is 2:1~3:1; peel off the graphene flake and potassium permanganate. The mass ratio is 1:8~1:9; the mass-volume ratio of KMnO ₄ to H ₂ O ₂ is 1:1~2:1 g/mL.

In step (1), the mass-to-volume ratio of graphene oxide to hydrazine hydrate is 0.5:1 to 1:1 g/mL.

In step (2), the mass ratio of the 3D-G to KMnO is ₁ :8 to 1:9; the mass to volume ratio of the 3D-G to H ₂ O is _1:30 to 1:35 g/ mL.

In step (2), the evaporation is to completely evaporate the liquid by continuous stirring at 85-90°C.

In step (3), the mass ratio of 3D-G to GQDs is 1:1~1.2:1.

In step (3), in the GQDs/3D-G composite dispersion, the concentrations of 3D-G and GQDs are 1.8-2 mg/mL.

In step (4), the mass ratio of the ammonium persulfate to the aniline-containing monomer is 2:1 to 2.5:1.

In step (4), the volume ratio of the N,N-dimethylacetamide to the dilute HCl solution is 1:4 to 1:5.

In step (4), in the polyaniline solution, the concentration of polyaniline is 3.8-4 mg/mL.

2. Structure and morphology of layer-by-layer self-assembled GQDs/3D-G/PANI composite films

Fig. 1, Fig. 2, Fig. 3 are SEM images of the self-assembled GQDs/3D-G/PANI composite films with different layers. Figure 1A is an image of the assembled first layer of PANI, denoted as (GQDs/3D-G/PANI) _0.5 , it can be found that the PANI particles are loosely distributed on the ITO surface, showing a small PANI loading. Next, by assembling and adsorbing the GQDs/3D-G layer, the complete assembly of the first layer of the film was completed, which is denoted as (GQDs/3D-G/PANI) ₁ , and its SEM image is shown in Figure 1B. 3D-G coverage, it can be observed that GQDs/3D-G and PANI are loosely covered on the ITO surface. Due to the low amount of loaded PANI and GQDs/3D-G, the coverage of the ITO surface is also low at this time. Figure 2A is the SEM image of (GQDs/3D-G/PANI) ₅ , and it can be observed that with the increase of the self-assembled layer, the self-assembled film becomes denser and basically covers the surface of ITO. Figure 2B is the image when the number of self-assembled layers reaches 10. It is found that at this time (GQDs/3D-G/PANI) ₁₀ particles are attached to the ITO surface uniformly and interconnected, and the network structure is obvious. Judging from the microscopic morphology, the formation of The abundant nanopores, which are favorable for ion adsorption and movement, can support good electrochemical activity and catalytic performance. With the progress of the self-assembly process, when the number of film layers was further increased to 12 and 15 layers, the GQDs/3D-G and PANI started to aggregate obviously, as shown in Figure 3A, 3B.

3. Electrocatalytic performance of layer-by-layer self-assembled GQDs/3D-G/PANI composite films

Fig. 4 and Fig. 5 are films with different layers (GQDs/3D-G/PANI) _n (n=0, 0.5, 1, 5, 10, 15) assembled on the surface of ITO in phosphate buffer solution (PBS). , 0.1 M, pH=7.4) in the CV curve at a scan rate of 0.05 V s ⁻¹ . It can be seen from Figure 2 that the two CV curves of bare ITO and (GQDs/3D-G/PANI) _0.5 do not have obvious characteristic peaks, which is mainly due to the scarcity of electroactive materials on ITO. In Figure 3, it can be seen that (GQDs/3D-G/PANI) ₁ appears a pair of redox peaks at 0.05V and -0.2V, corresponding to the redox peaks of polyaniline. In addition, with the increase of self-assembled layers, the loading of electroactive materials on ITO increases, and the redox current of self-assembled films increases; but when the number of self-assembled layers reaches 15 layers, the redox current begins to decrease significantly (Fig. 3), which may be because the film is too dense, preventing the transfer of electrons from the electrolyte to the ITO surface.

Figure 6 shows the films (GQDs/3D-G/PANI) with different layers assembled on the surface of ITO according to the present invention. _n (n=1, 5, 10, 15) were added to PBS solution (0.1M, pH=7.4) by adding 10 CV curves at a scan rate of 0.05 V s ⁻¹ after ⁻⁴ M of H ₂ O ₂ . Figure 6 shows that the CV peak current of (GQDs/3D-G/PANI) _n is significantly increased relative to the peak current of Figure 5 . The peak currents increased by 2.2%, 23.75%, 84.7% and 25.3% for (GQDs/3D-G/PANI) _n with n=1, 5, 10, and 15, respectively, indicating that (GQDs/3D-G/PANI) _n The ITO surface has an obvious catalytic decomposition effect on H ₂ O ₂ , among which (GQDs/3D-G/PANI) ₁₀ has the highest response to H ₂ O ₂ . At the same time, the redox current of (GQDs/3D-G/PANI) ₁₅ is significantly reduced, because the dense surface restricts electron transfer.

In summary, the present invention firstly prepares three-dimensional network graphene (3-DG) and graphene quantum dots (GQDs), and then uses GQDs to self-assemble on the 3D-G surface to prepare a GQDs/3D-G composite system. Finally, with the strong electrostatic force between the electropositive polyaniline (PANI) solution and the electronegative GQDs/3D-G composite dispersion solution and the π-π interaction between the benzene ring structures as the driving force, in the hydroxyl-functionalized ITO A layer-by-layer self-assembled GQDs/3D-G/PANI composite film was constructed on the surface, the polyaniline could be firmly attached to the 3D network graphene layer, and the graphene quantum dots assisted the interaction between the 3D graphene sheets and the polyaniline particles. close contact, significantly reduced agglomeration, and _exhibited good electrochemical catalytic activity for _H2O2 .

Description of drawings

Fig. 1, Fig. 2, Fig. 3 are SEM images of the self-assembled GQDs/3D-G/PANI composite films with different layers.

Figure 4 and Figure 5 are the CV curves of the self-assembled GQDs/3D-G/PANI composite films with different number of layers in PBS solution.

Figure 6 shows the comparison of the CV curves of the self-assembled GQDs/3D-G/PANI composite films with different layers in PBS solution for the catalytic decomposition of H ₂ O ₂ .

Detailed ways

The preparation of the layer-by-layer self-assembled GQDs/3D-G/PANI composite films with different layers of the present invention will be further described below through specific examples.

Example 1

(1) Preparation of 3DG: The expanded graphite was sonicated in a DMF solution for 24 h, filtered, washed, and dried to obtain a liquid-phase ultrasonically exfoliated graphene sheet. Then 1 g graphene flakes were added to the mixed acid (90 mL concentrated sulfuric acid and 30 mL concentrated phosphoric acid) at 0~5 °C, while maintaining the temperature of the ice-water bath, ₉ g KMnO was slowly added in constant stirring, and then heated to 50 °C with continuous stirring React for 12 hours. After the above reaction, at room temperature, 200 mL of ice water and 5 mL of 30% H ₂ O ₂ solution were added to the mixed solution, and the color of the solution changed to gold. The mixture was centrifuged, washed, and dried to obtain graphene oxide. Then take 0.1 g of graphene oxide and disperse it in 100 mL of water, add ammonia water until the pH of the solution reaches 12, then add 0.15 mL of hydrazine hydrate, transfer the mixed solution to a hydrothermal reactor, and react at 180 °C for 12 h. After the reaction, the product is filtered, washed and dried to obtain three-dimensional network graphene.

(2) Preparation of GQDs: Weigh 0.1 g of 3D-G and disperse it in 120 mL of concentrated sulfuric acid, stir magnetically at 5 °C for 10 min, slowly add 0.8 g KMnO ₄ , heat to 150 °C, and then condense at a constant temperature for 24 h. , the reaction solution was slowly poured into a rapidly stirring 5°C ice-water bath; cooled to room temperature, and 3 mL of H ₂ O ₂ was added dropwise to it to obtain a bright yellow GQDs solution. After removing the condensation device, the liquid was completely evaporated under continuous stirring at 85 °C to obtain brown GQDs as solids. The obtained GQDs were dispersed in ultrapure water, filtered, dialyzed and freeze-dried to obtain GQDs powder.

(3) Preparation of GQDs/3D-G composite dispersion: Add 15 mg 3D-G and 15 mg GQDs to 15 mL of diluted HCl solution (pH=3.0, 0.01 M) and stir until uniformly mixed, adjust the dispersion with ammonia water The pH of the mixed solution was 6.0, and the mixed solution was ultrasonically treated for 30 min to obtain the GQDs/3D-G composite dispersion.

(4) Preparation of PANI solution: 15.0 g of ammonium persulfate ((NH4) ₂ S ₂ O ₈ ) was added to 60 mL of HCl solution (1.0 M) containing 6.0 g of aniline monomer distilled under reduced pressure to synthesize the polymer. aniline. The mixture was stirred at 0 °C for 24 h, then the product was filtered and washed sequentially with dilute HCl solution, ethanol and deionized water. After the obtained product was soaked in ammonia water (1.0 M) for 10 h, the obtained polyaniline was heated at 50 °C. Vacuum dry. Take 200 mg of dry dark green polyaniline and add it to 10 mL of N,N-dimethylacetamide, stir for 2 h to obtain a uniformly dispersed dark blue solution, and then add it to 40 mL of dilute HCl solution (pH = 3.0) Mix evenly in the medium, and then a stable aqueous dispersion conductive polyaniline solution can be obtained.

(5) Preparation of layer-by-layer self-assembled GQDs/3D-G/PANI composite films:

① Preparation of hydroxyl functionalized ITO substrate

The ITO was cut into 2 cm slices, washed thoroughly by sonication in ethanol, acetone, and deionized water, and dried with nitrogen. To generate a uniform distribution of hydroxyl groups on the ITO surface, the ITO plate was placed in a solution containing 10 mL H ₂ O ₂ , 10 mL NH ₄ OH and 50 mL H ₂ O, oxidized at 80 °C for 30 min, and then heated in H ₂ Ultrasonic treatment for 30 min in a mixture of O/HCl/H ₂ O ₂ (6:1:1, v/v/v); finally rinsed thoroughly with high-purity water, dried with nitrogen, moved to an oven at 100 °C, and dried for 12 h spare.

② Layer-by-layer self-assembly of GQDs/3D-G/PANI on ITO substrate

A piece of hydroxyl-functionalized ITO was immersed in the PANI solution for 2 h, taken out for washing with water, and dried by blowing nitrogen gas at room temperature. A layer of PANI is formed on the ITO, which can be expressed as (GQDs/3D-G/PANI) _0.5 .

Example 2

Preparation of layer-by-layer self-assembled GQDs/3D-G/PANI composite films: A piece of hydroxyl-functionalized ITO was immersed in the PANI dispersion for 2 h, taken out for rinsing with water, and dried by blowing nitrogen at room temperature. To induce the assembly of GQDs/3D-G layers on the glass surface, the glass was immersed in the GQDs/3D-G dispersion for 2 h, and a layer of GQDs/3D-G/PANI was formed on ITO, which can be expressed as (GQDs/3D -G/PANI) ₁ .

Preparation of other materials: the same as in Example 1.

Example 3

Preparation of layer-by-layer self-assembled GQDs/3D-G/PANI composite films: A piece of hydroxyl-functionalized ITO was immersed in the PANI dispersion for 2 h, taken out for rinsing with water, and dried by blowing nitrogen at room temperature. To induce the assembly of GQDs/3D-G layers on the glass surface, the glass was immersed in the GQDs/3D-G dispersion for 2 h, and a layer of GQDs/3D-G/PANI was formed on ITO, which can be expressed as (GQDs/3D -G/PANI) ₁ ; According to the similar process, repeated 5 times, after 20 h, the (GQDs/3D-G/PANI) ₅ composite film was prepared by layer-by-layer self-assembly on top of ITO.

Preparation of other materials: the same as in Example 1.

Example 4

Preparation of layer-by-layer self-assembled GQDs/3D-G/PANI composite films: A piece of hydroxyl-functionalized ITO was immersed in the PANI dispersion for 2 h, taken out for rinsing with water, and dried by blowing nitrogen at room temperature. To induce the assembly of GQDs/3D-G layers on the glass surface, the glass was immersed in the GQDs/3D-G dispersion for 2 h, and a layer of GQDs/3D-G/PANI was formed on ITO, which can be expressed as (GQDs/3D -G/PANI) ₁ ; According to the similar process, repeated 10 times, and after 40 h, the (GQDs/3D-G/PANI) ₁₀ composite film was prepared by layer-by-layer self-assembly on top of ITO.

Preparation of other materials: the same as in Example 1.

Example 5

Preparation of layer-by-layer self-assembled GQDs/3D-G/PANI composite films: A piece of hydroxyl-functionalized ITO was immersed in the PANI dispersion for 2 h, taken out for rinsing with water, and dried by blowing nitrogen at room temperature. To induce the assembly of GQDs/3D-G layers on the glass surface, the glass was immersed in the GQDs/3D-G dispersion for 2 h, and a layer of GQDs/3D-G/PANI was formed on ITO, which can be expressed as (GQDs/3D -G/PANI) ₁ ; According to the similar process, repeated 12 times, after 48 h, the (GQDs/3D-G/PANI) ₁₂ composite film was prepared by layer-by-layer self-assembly on top of ITO.

Preparation of other materials: the same as in Example 1.

Example 6

Preparation of layer-by-layer self-assembled GQDs/3D-G/PANI composite films: A piece of hydroxyl-functionalized ITO was immersed in the PANI dispersion for 2 h, taken out for rinsing with water, and dried by blowing nitrogen at room temperature. To induce the assembly of GQDs/3D-G layers on the glass surface, the glass was immersed in the GQDs/3D-G dispersion for 2 h, and a layer of GQDs/3D-G/PANI was formed on ITO, which can be expressed as (GQDs/3D -G/PANI) ₁ ; According to the similar process, repeated 15 times, after 60 h, the (GQDs/3D-G/PANI) ₁₅ composite film was prepared by layer-by-layer self-assembly on the top of ITO.

Preparation of other materials: the same as in Example 1.

Claims (10)

1. A preparation method of a layer-by-layer self-assembled GQDs/3D-G/PANI composite film comprises the following process steps:

(1) preparation of 3D-G: dispersing graphene oxide in water, adding ammonia water to adjust the pH value of the solution to 12-13, adding hydrazine hydrate, transferring the solution to a hydrothermal reaction kettle, reacting for 11-12 hours at 180-185 ℃, filtering, washing and drying to obtain three-dimensional network graphene 3D-G;

(2) preparation of GQDs: dispersing 3D-G in concentrated sulfuric acid, stirring in ice water bath, and adding KMnO₄Condensing and reacting at constant temperature of 150-155 ℃ for 24-25H, cooling to room temperature, and then adding H₂O₂Obtaining bright yellow GQDs solution, evaporating the GQDs solution to obtain brown GQD solid, dissolving the GQDs solid in ultrapure water, and filtering, dialyzing, freezing and drying to obtain graphene quantum dot GQDs powder;

(3) preparing a GQDs/3D-G composite dispersion liquid: dispersing 3D-G and GQDs in HCl solution, stirring uniformly, adjusting the pH to 5.0-6.0 by using ammonia water, and carrying out ultrasonic treatment for 20-30 min to obtain a GQDs/3D-G composite dispersion liquid;

(4) preparation of PANI solution: adding ammonium persulfate into an HCl solution containing an aniline monomer, stirring for 24-25 h at 0-5 ℃, filtering, washing with dilute HCl, ethanol and deionized water in sequence, soaking in ammonia water for 10-12 h, and vacuum drying to obtain polyaniline; adding polyaniline into N, N-dimethylacetamide, stirring for 2-2.5 h to obtain a dark blue solution, adding the dark blue solution into dilute HCl, and uniformly mixing to obtain a stable aqueous dispersion conductive polyaniline solution;

(5) preparing a layer-by-layer self-assembled GQDs/3D-G/PANI composite film: dipping the hydroxyl functionalized ITO in PANI solution for 2-2.5 h, taking out, washing with water, drying at room temperature by blowing nitrogen, dipping the ITO in GQDs/3D-G composite dispersion liquid for 2-2.5 h to form a layer of GQDs/3D-G/PANI on the ITO, and marking as (GQDs/3D-G/PANI)₁(ii) a Repeating the cycle, and self-assembling the ITO layer by layer (GQDs/3D-G/PANI)_nAnd (3) compounding the film.

2. The method for preparing a layer-by-layer self-assembled GQDs/3D-G/PANI composite film according to claim 1, wherein the method comprises the following steps: in the step (1), the preparation method of the graphene oxide comprises the following steps: ultrasonically treating expanded graphite in a DMF (dimethyl formamide) solution for 20-24 hours, filtering, washing and drying to obtain a liquid-phase ultrasonic stripping graphene sheet, adding the stripping graphene sheet into a mixed acid of concentrated sulfuric acid and concentrated phosphoric acid at 0-5 ℃, and adding KMnO (KMnO) under stirring₄Heating to 50-55 ℃, stirring for reaction for 11-12H, and then adding ice water and H into the mixture at room temperature₂O₂The solution is centrifuged, washed and dried to obtain graphene oxide, wherein the color of the solution is changed into golden yellow; the volume ratio of concentrated sulfuric acid to concentrated phosphoric acid in the mixed acid is 2: 1-3: 1; the mass ratio of the stripped graphene sheet to the potassium permanganate is 1: 8-1: 9; KMnO₄And H₂O₂The mass-to-volume ratio of (A) is 1: 1-2: 1 g/mL.

3. The method for preparing a layer-by-layer self-assembled GQDs/3D-G/PANI composite film according to claim 1, wherein the method comprises the following steps: in the step (1), the mass-to-volume ratio of the graphene oxide to the hydrazine hydrate is 0.5: 1-1: 1 g/mL.

4. The method for preparing a layer-by-layer self-assembled GQDs/3D-G/PANI composite film according to claim 1, wherein the method comprises the following steps: in the step (2), the 3D-G is reacted with KMnO₄The mass ratio of (A) to (B) is 1: 8-1: 9; the 3D-G and H₂O₂The mass-to-volume ratio of (A) is 1: 30-1: 35 g/mL.

5. The method for preparing a layer-by-layer self-assembled GQDs/3D-G/PANI composite film according to claim 1, wherein the method comprises the following steps: in the step (2), the evaporation is to completely evaporate the liquid by continuously stirring at 85-90 ℃.

6. The method for preparing a layer-by-layer self-assembled GQDs/3D-G/PANI composite film according to claim 1, wherein the method comprises the following steps: in the step (3), the mass ratio of the 3D-G to the GQDs is 1: 1-1.2: 1.

7. The method for preparing a layer-by-layer self-assembled GQDs/3D-G/PANI composite film according to claim 1, wherein the method comprises the following steps: in the step (3), the concentration of the GQDs and the concentration of the GQDs in the GQDs/3D-G composite dispersion liquid are 1.8-2 mg/mL.

8. The method for preparing a layer-by-layer self-assembled GQDs/3D-G/PANI composite film according to claim 1, wherein the method comprises the following steps: in the step (4), the mass ratio of the ammonium persulfate to the aniline-containing monomer is 2: 1-2.5: 1.

9. The method for preparing a layer-by-layer self-assembled GQDs/3D-G/PANI composite film according to claim 1, wherein the method comprises the following steps: in the step (4), the volume ratio of the N, N-dimethylacetamide to the dilute HCl solution is 1: 4-1: 5.

10. The method for preparing a layer-by-layer self-assembled GQDs/3D-G/PANI composite film according to claim 1, wherein the method comprises the following steps: in the step (4), the concentration of polyaniline in the polyaniline solution is 3.8-4 mg/mL.

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